User interfaces have traditionally relied on input devices such as keyboards, which require physical manipulation by a user. Increasingly, however, it is desired to detect and monitor the physical positions and movements of users within a scene or environment, and to respond to more natural user actions.
Speech recognition may be used in some situations for recognizing user commands. However, it may sometimes be desired to reliably detect or recognize other types of sounds, which may be non-verbal, and to respond to such sounds. In particular, some types of devices may respond to user-generated taps or double-tabs, such knocking on a surface, snapping the fingers of a hand, or clapping two hands together.